The present invention relates to vehicle navigation systems providing directional guidance at branch points such as intersections along with other route guidance while the vehicle travels along a route determined by a search conducted in response to input of place data such as destination data or transit points.
In the past, various types of route guidance systems have been proposed to facilitate driving along a road unfamiliar to the driver. In such systems, the driver is guided along a route to a destination after inputting the destination. Some of the route guidance systems provide directional guidance when the vehicle passes through branch points such as intersections.
As shown in FIG. 1 for an example of a guidance route going to or through a destination "B" wherein the guidance route branches to the right at a point P1 and further branches to the left at a point P2 relatively near to the point P1, the prior art directional guidance is as follows: While approaching branch point P1, the guidance system has an option of displaying either a first sign of destination "C" with an arrow pointing straight ahead or a second sign of destinations "A" and "B" with an arrow pointing to the right and, in this example, chooses to display the second sign of "A" and "B" with the arrow pointing to the right as shown in FIG. 2(a) as the guidance sign. Next while approaching the branch point P2, the guidance sign for "B" with the arrow pointing to the left is displayed as shown in FIG. 2(b).
In the prior art directional guidance displaying signs with two or more destination names, all the destination names on such signs are displayed, for example, "A" and "B" are displayed at the first branch point P1 where guidance is provided. Because two or more destination names are displayed at such branch points, it is often difficult to read all the destination names with a brief glance, for example, the driver may miss the instruction to turn right to "B" until the vehicle has actually passed the first branch point P1. Also when the next branch point P2 closely follows point P1, the guidance system displays the sign for destination "B" with the left arrow only briefly before reaching the branch point P2.
Prior art route guidance systems have displayed the distance and time required to the destination. In case an expressway is included in the guidance route, the name of the nearest interchange ("IC") is displayed while driving along the expressway, but the name of the IC where the vehicle should exit from the expressway is not displayed until the vehicle is within a given distance of the IC. Guidance information displayed while on an expressway is skimpy, and the driver often cannot obtain guidance even when he or she wants to confirm the guidance information.
Also, prior art route guidance systems have displayed the expected time of arrival at the destination as calculated from a preset average vehicle velocity. However, there may be some deviation in the suggested time of arrival depending upon conditions or situations of the road leading to the destination.
It is an object of the present invention to provide a navigation system which can ensure easy to understand and reliable direction guidance.
It is another object of the present invention to provide a navigation system by which it is possible to determine whether or not a vehicle should be driven in accordance with information on a specific destination at a first guide branch point.
It is still another object of the present invention to provide a navigation system by which it is possible to identify information of a direction to be driven in advance.
It is a further object of the present invention to provide a navigation system which, while driving along an expressway or a toll road, displays on a guidance screen the name of an IC where the vehicle should exit from the expressway or toll road.
It is a still further object of the present invention to provide a navigation system which informs the driver of information on driving of the vehicle and of the expected time of arrival.